Strong muscles of the abdominal wall, i.e., abdominals or “abs,” are important for a number of health reasons including support of the back and protection thereof from stress. Exercises for strengthening the abdominals range from relatively simple equipmentless exercises such as the sit-up and the crunch to elaborate machine assisted exercises employing expensive machines. To be effective, such exercises must isolate and work the abdominals while not putting stress on the lower back or engaging the hip flexor muscles. In this regard, many people suffer from lower back pain and while strengthened abdominals can help, care should be taken to ensure that the exercise used to strengthen the abdominals does not itself place further stress on the back.
Sit-ups exercise the full trunk and thus work the thigh flexor muscles as well as the abdominals. In fact, sit-ups work the former more than the latter and thus are less than fully effective in exercising the abdominals. Further, because of the muscles worked, sit-ups can place substantial stress on the low back. Crunches are better than sit-ups insofar as isolating the abdominals but because the movement in performing a crunch is from a position with the back flat on the floor to a crunch position where just the head and shoulders are raised from the floor, the range of motion to which the abdominals are subjected is limited.
Most other exercises for the abdominals, including those performed using exercise machines, rely on the movements associated with sit-ups and crunches and suffer the same basic disadvantages.
Considering some of the patented art in this field, U.S. Pat. No. 5,803,884 to Sharp discloses an abdominal exercise apparatus including an adjustable curved back support against which the lower back of the user rests. The apparatus is used to produce an exercise which is said to isolate, stretch, work and develop the muscles of the abdominal wall, while eliminating in the exercise the use of thigh flexors and the pain that thigh flexors can cause. This patent also includes a detailed discussion of the disadvantages of the prior art including sit-ups and crunches. However, the apparatus disclosed in the Sharp patent itself suffers important disadvantages including the lack of neck support (thus subjecting the neck to possible strain), lack of upper torso support, the apparent lack of easy portability, the lack of versatility in that the apparatus can only be used in abdominal exercise, and the inherent limitations on the capability thereof in increasing the tension exerted on the abdominals.
Other patents of interest in this general field include the following U.S. Pat. No. 5,882,284 to Cayne, U.S. Pat. No. 5,947,876 to Willey, II, U.S. Pat. No. 5,755,647 to Watnik, U.S. Pat. No. 5,931,769 to Nunig and U.S. Pat. No. 5,100,131 to Fong.